This invention relates to a method of producing a plurality of identical ring-shaped metal parts from a rod-shaped blank by repetition of a sequential combination of upsetting working and shearing working.
Die forging has been employed to produce ring-shaped metal parts of relatively high strength and high precision, such as intermediates of gears for instance.
In a conventional ring producing method of this type, a disk-shaped blank is first formed into an intermediate having the shape of a shallow dish by die forging, using a stationary die formed with a circular recess having a diameter corresponding to the outer diameter of the ring-shaped metal part to be produced and a movable die formed with a short cylindrical projection having a diameter corresponding to the inner diameter of the ring-shaped part. That is, the blank is axially compressed between the two dies and, hence, is forced to radially expand into an annular space given by partial intrusion of the projection of the movable die into the recess of the stationary die. The intermediate has an annular brim portion greater in thickness than the circular bottom portion.
This intermediate is transferred into another press which is equipped with a shearing die having a central hole having a diameter which corresponds to the inner diameter of the intermediate, and the circular bottom portion of the intermediate is punched out by the action of a shearing punch fittable into the hole of the shearing die to leave the annular brim portion of the intermediate as the intended ring-shaped metal part. The separated bottom portion of the intermediate is disposed of as scrap.
From a commercial point of view, it is a disadvantage of this ring producing method that a considerable portion of the material must be scrapped with extra labor costs for recovery and handling of the scrap portions of the individual intermediates. Besides, there is the need for transferring the intermediates from the forging machine to the shearing machine. Furthermore, there is a possibility of suffering from an insufficiency in the precision of the ring-shaped parts by reason of some errors in the alignment of the individual intermediates with the shearing die.